Peirce's Logic - Article in the Stanford Encyclopaedia of Philosophy, by Eric Hammer. Why Aristotelian Logic does not Work - An essay at Abelard.org outlining an argument against Aristotelian syllogistic. Logic - An online textbook by Garth Kemerling, explaining the basic elements of elementary logic at an undergraduate level. Symbolic Logic - Online resources provided to supplement undergraduate course taught by Peter Suber. Good collection of handouts. Tips on Translating English into First-Order Logic - An introductory guide by Peter Suber. Frege's Theorem - Article in the Stanford Encylcopaedia of Philosophy, entitled `Frege's Logic, Theorem, and Foundations for Arithmetic'. Discusses the 1980 discovery of Crispin Wright that Frege's work of the Grundgesetze can be carried out in second-order logic with Hume's principle. Humboldt State University: Argumentation and Critical Thinking Tutorial - Jay VerLinden's resource offering reviews and tests on important concepts in formal logic.